Memory circuit arrangement and method for the production thereof

ABSTRACT

A memory circuit arrangement and fabrication method thereof are presented in which the parts of the memory circuit arrangement are situated on two different substrates. An integrated memory cell array is situated on one substrate. An integrated control circuit that controls access to the memory cells is situated on the other (logic circuit) substrate. The control circuit controls sequences when reading, writing or erasing content of a memory cell. The logic circuit substrate also contains a CPU and encryption coprocessor. The memory circuit contains a sense amplifier, with the aid of which the memory state of a memory cell can be determined, and a decoding circuit that selects a word or bit line.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.12/258,728 filed on Oct. 27, 2008, which is continuation application ofU.S. Ser. No. 11/251,355 filed Oct. 14, 2005, which is a continuation ofInternational Application PCT/EP2004/050322, filed on Mar. 17, 2004,which claims the benefit of priority to German Patent Application DE 102003 10319271.9 filed on Apr. 29, 2003, all of which are hereinincorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a memory circuit arrangement having asubstrate for a memory cell array and having a substrate for a logiccircuit for driving the memory cell array.

BACKGROUND

In memory circuit arrangements, two kinds of memory circuits exist:nonvolatile memory circuits and volatile memory circuits. Nonvolatilememory circuits return their memory content even after a supply voltageof the memory circuit has been switched off. Examples of nonvolatilememory circuits include ROM circuits (Read Only Memory) or EEPROMcircuits (Electrically Erasable Programmable Read Only Memory). Volatilememory circuits lose their memory content after a supply voltage for thememory circuit has been switched off. Examples of volatile memorycircuits include DRAM circuits (Dynamic Random Access Memory) or SRAMcircuits (Static Random Access Memory).

What is common to these memory circuits is that both the memory cellarray and the logic circuit are situated on one substrate, e.g. on asemiconductor substrate, in particular on a silicon substrate, see DE198 19 542, by way of example. In so-called embedded systems, the memorycircuit arrangements are fabricated together with a processor on onesubstrate. On the other hand, there are also so-called system-in-packagecircuits, in the case of which a memory chip and a processor chip arearranged in a circuit housing. In the case of so-called multi-chipmodules, too, one circuit contains a plurality of “standard” circuits,e.g. a memory circuit and a processor circuit.

However, fabrication of memory circuit arrangements is relativelycomplicated and thus costly. Accordingly, a memory circuit arrangementthat can be produced simply and cost-effectively is desirable.

SUMMARY

By way of introduction only, a memory circuit arrangement and simple andcost-effective method of fabrication thereof is presented.

In one embodiment, a memory circuit arrangement comprises a cell arraysubstrate and a logic circuit substrate that is a different substratethan the cell array substrate. The cell array substrate has anintegrated memory cell array contained in a memory circuit. Theintegrated memory cell array includes memory cells. The logic circuitsubstrate has an integrated logic circuit that controls access to thememory cells. The logic circuit includes a control circuit contained inthe memory circuit, the control circuit controlling sequences when atleast one of reading or writing content of a memory cell of the memorycell array, and/or a decoding circuit contained in the memory circuit,the decoding circuit selects, in a manner dependent on an address datum,a word line or a bit line connected to a plurality of memory cells ofthe memory cell array.

In another embodiment, a method for producing an integrated circuitarrangement is presented, in which the following steps are performedwithout any restriction by the order specified: fabricating anintegrated memory cell array on a memory cell array substrate using afirst sequence of method steps; fabricating an integrated logic circuitthat provide basic functions of the memory cell array on a logic circuitsubstrate, which is separate from the memory cell substrate, using asecond sequence of method steps, which differs from the first sequence;and arranging the integrated memory cell array and the integrated logiccircuit to form a memory circuit arrangement. The logic circuit includesa control circuit contained in the memory circuit, the control circuitcontrolling sequences when at least one of reading or writing content ofa memory cell of the memory cell array, and/or a decoding circuitcontained in the memory circuit, the decoding circuit selects, in amanner dependent on an address datum, a word line or a bit lineconnected to a plurality of memory cells of the memory cell array.

The foregoing summary has been provided only by way of introduction.Nothing in this section should be taken as a limitation on the followingclaims, which define the scope of the invention.

BRIEF DESCRIPTION OF THE FIGURES

The application will be described below in greater detail on the basisof preferred embodiments and with reference to the accompanyingdrawings, in which:

FIG. 1 shows the division of circuit parts of a circuit arrangementbetween two substrates with a small number of connecting locationsbetween the substrates,

FIG. 2 shows the division of circuit parts of a circuit arrangementbetween two substrates with a multiplicity of connecting locationsbetween word lines and bit lines,

FIG. 3 shows a cross section through a substrate stack having threesubstrates during the production of a circuit arrangement,

FIG. 4 shows a plan view of a substrate stack having two substratesconnected by means of a rapid chip mounting technique, and

FIG. 5 shows a cross section through the substrate stack having twosubstrates.

DETAILED DESCRIPTION

The overall production outlay depends on the outlay for the productionof a specific chip area in a memory circuit arrangement. By virtue of askilful division of the units of a memory circuit arrangement, forexample, on account of technological considerations, it is possible toachieve, in a simple manner, a considerable reduction of the productioncosts per chip area, even when taking account of an additional assemblyoutlay with which the separately fabricated constituent parts areconnected to one another. By way of example, if the number of methodsteps for producing a subcircuit decreases by a third in comparison withthe production of the memory circuit arrangement on only a singlesubstrate, then the method implementation becomes considerably simpler.The production outlay relating to a chip area is then reduced for eachsubcircuit for example by more than half in comparison with theproduction outlay per chip area when producing the memory circuitarrangement on a single substrate. Addition of the production outlay forthe two partial chip areas results in a production outlay that isconsiderably less than the production outlay which results if theintegrated circuit arrangement is produced on only one substrate.

Therefore, the memory circuit arrangement is presented that contains acell array substrate, which carries an integrated memory cell arraycomprising a multiplicity of memory cells. Each memory cell contains atleast one transistor, e.g. a floating gate transistor, or alternativelya transistor and a storage capacitor. Moreover, the memory circuitarrangement contains a logic circuit substrate, which carries at leastone integrated logic circuit for controlling the access to the memorycells in the context of the basic functions of the memory circuitarrangement. The basic functions include reading, writing or erasing thecontent of one or more memory cells of the memory cell array. In oneconfiguration, a selection of specific memory cells of the memory cellarray in a manner dependent on an address datum present at the memorycircuit also concerns the basic function of the memory circuitarrangement.

In one embodiment, the logic circuit substrate is a different substratethan the cell array substrate. In particular, the integrated circuitarrangements arranged on the two substrates have been fabricated inmutually separate production methods.

In one embodiment, the cell array substrate has substrate surfaces whichsurround only the cell array substrate and not the logic circuitsubstrate on all sides. Conversely, the logic circuit substrate hassubstrate surfaces which surround only the logic circuit substrate andnot the cell array substrate on all sides. The substrate surfaces are,in particular, separating areas or polished separating areas.

In another embodiment, the memory cells of the memory cell array arevolatile memory cells. In an alternative development, the memory cellsof the memory cell array are nonvolatile memory cells, such as flashmemory cells, in the case of which a multiplicity of memory cells areerased during each erasing operation. Nonvolatile memory cells exhibitconsiderable technological differences in the production of the cellarray and in the production of peripheral circuits. The differencesbecome greater with smaller minimum feature sizes and with theutilization of new memory principles, for example in the case offerroelectric or magnetoresistive memory cells or in the case of memorycells that utilize a change between an amorphous and a crystalline phasefor storage.

The logic circuit substrate may carry a control circuit, which controlssequences when reading, sequences when writing to, and sequences whenerasing a memory cell of the memory cell array. In particular, thesequence of control signals is ensured by means of the control circuit.By way of example, for NOR type nonvolatile memory circuits, the controlcircuit is referred to as FACE (Flash Algorithmic Control Engine).Similar central control circuits for controlling the function of thememory circuit are present for NAND and other types of integratedcircuits.

The logic circuit substrate may contain a sense amplifier circuit, withthe aid of which the memory state of a memory cell can be determined.The logic circuit substrate may also contain at least one decodingcircuit which selects, from an address datum, a collective line that isconnected to a plurality of memory cells of the memory cell array, butnot to all the memory cells of the memory cell array. A collective lineconnected to memory cells of a row of memory cells of the memory cellarray is also referred to as a word line. The word lines are connectede.g. to the gate electrodes of transistors of the memory cells. Acollective line connected to memory cells of a column of memory cells ofthe memory cell array is also referred to as a bit line. The bit linesare connected e.g. to the source/drain zones of field effect transistorsof the memory cells. Moreover, electrically conductive connections arepresent between the cell array substrate and the logic circuit substratefor each collective line. These connections can be a solderingconnection, an adhesive connection, a welding connection, a bondingconnection, a connection produced by curing a mixture containing asolvent, for example in accordance with EP 0 610 709 A1, or ametallization connection penetrating through the entire thickness of thememory cell substrate or the entire thickness of the logic circuitsubstrate, as shown in, for example, DE 199 04 751 C1.

In this case, the number of connections between the substrates dependson the number of word lines and/or the number of bit lines. Thus, by wayof example, the number of connections is more than 1000, more than 2000or more than 3000, depending on the storage capacity of the memory cellarray.

The logic circuit substrate may carry a circuit arrangement of at leastone processor which is suitable for processing program instructions, inparticular for processing program instructions stored in the memory cellarray. The processor contains, inter alia, an arithmetic logic unit anda control unit, in which a micro program, for example, is executed. Inthis case, the logic circuit substrate may contain a circuit arrangementfor two processors, namely for a main processor and a coprocessor. Thecoprocessor is, for example, a processor that executes an encryptionalgorithm for encrypting data. In one configuration, a circuitarrangement having a memory circuit arrangement, processor andcoprocessor is incorporated into a so-called smart card having athickness of less than 2 mm.

The cell array substrate may carry at least one sensor, for example, avoltage sensor or a current sensor. The cell array substrate may containan analog-to-digital converter, for example for converting the analogoutput signals generated by a sensor into a digital datum.

A main area of the cell array substrate and a main area of the logiccircuit substrate may lie in two planes parallel to one another,preferably with overlapping in the direction of the normal to one mainarea. In this case, a main area, in contrast to an edge area, is an areacontaining a considerably larger amount of area than the edge area. Inthis development, the two substrates and, if appropriate, also furthersubstrates of the circuit arrangement are stacked one above the other.In contrast to previous stacks of substrates, however, in the case ofthe development, assemblies of a memory circuit arrangement lie ondifferent substrates of the substrate stack.

As an alternative, it is also possible to use a carrier substrate onwhich, by way of example, a plurality of substrates situatedtransversely with respect to the carrier substrate are lined up. In thiscase, a main area of the cell array substrate is situated transverselywith respect to a main area of the logic circuit substrate.

A method for producing the memory circuit arrangement includesfabricating an integrated memory cell array on a memory cell substrateby means of a first sequence of method steps, fabricating an integratedlogic circuit for providing basic functions of the memory cell array ona logic circuit substrate separate from the memory cell substrate, bymeans of a second sequence of method steps, which differs from the firstsequence, and arranging the integrated memory cell array and theintegrated circuit arrangement to form a memory circuit arrangement.

In particular, the two sequences of method steps relate to differentproduction technologies, for example production technologies withmutually different minimum feature sizes. The first sequence of methodsteps can be performed before the second sequence of method steps iscarried out. Conversely, however, it is also possible for the secondsequence of method steps to be carried out before the first sequence ofmethod steps. It is also possible to simultaneously carry out the twosequences of method steps at the same production site or at differentproduction sites. When said sequences of method steps are carried out atthe same production site, e.g. different machines are used for methodsteps of the two methods. When the same machines are utilized, themethod steps of different sequences are performed in succession.

In one embodiment, the first sequence contains method steps which areparticularly suitable for the production of a memory cell array andwhich are not required in the production of the logic circuit.Similarly, the second sequence may contain method steps which areparticularly suitable for the production of logic circuits and which arenot required in the production of a memory cell array. This proceduregives rise to a method which comprises two partial methods and theproduction outlay of which in total is less than a method in which boththe memory cell array and the logic circuit have to be produced by meansof the same technology or in which, with regard to the logic circuit orto the memory cell array, specific compromises have to be made in theproduction of the memory cell array or in the production of the logiccircuit, respectively.

Turning now to the figures, FIG. 1 shows circuit blocks of a circuitarrangement 10. Circuit blocks of a memory circuit are situated in aleft-hand part 12 of the circuit arrangement 10. Additional circuitsthat are provided in addition to the memory circuit in the circuitarrangement 10 are situated in a right-hand part 14 of the circuitarrangement 10. However, the additional circuits utilize the memorycircuit during operation of the circuit arrangement 10.

The memory circuit is, for example a memory circuit having memory cellsthat store charge in nonvolatile fashion or having memory cells thatstore charge in volatile fashion. In the exemplary embodiment, thememory circuit contains two or more memory cell arrays 16, 18 in whichmemory cells are arranged in rows and columns in a matrix-type manner.Memory cells of a row are connected by word lines leading to word linedriver transistors 20, 22 at the left-hand edge of the memory cell array16 and 18, respectively. Bit lines, on the other hand, connect thememory cells of a column of a memory cell array 16 and 18, respectively,and lead to bit line driver transistors 24 at the lower edge of thememory cell array 18. The driver transistors 20 to 24 serve for levelconversion.

A switching transistor group 26 is arranged between the two memory cellarrays 16 and 18. A further switching transistor group 28 is situatedabove the memory cell array 16. The switching transistors of theswitching transistor groups 26 and 28 serve for the connection ofinternal bit lines in a memory cell array, or so-called local bit lines,to bit lines that run over or through a plurality of memory cell arrays16, 18. The word line driver transistors 20 and the word line drivertransistors 22 are driven by a word line decoding circuit 30 and by aword line decoding circuit 32, respectively. The decoding circuit 30 and32 selects a word line in a manner dependent on an address datum forspecifying a word line, for example by the application of a voltage onlyto the selected word line.

The bit line driver transistors 24 are driven by a bit line decodingcircuit, which selects a bit line in a manner dependent on an addressdatum for designating a bit line. The bit line decoding circuit is oneof a plurality of logic circuits 34 for providing the basic functions ofthe memory circuit. The logic circuits 34 also include, by way ofexample, a so-called sense amplifier, with the aid of which the memorystate of a memory cell can be determined.

The memory circuit furthermore includes a charge pump 36, which can beused to generate voltages required for erasing or writing to the memorycells of the memory cell array. Moreover, the memory circuit contains,for providing its basic functions, a control circuit 38, which performssuperordinate control functions in the memory circuit. This controlincludes, for example, control of programming, reading and/or erasing,and control of the decoding circuits 30, 32, of the logic circuits 34and/or of the charge pump 36.

The right-hand part of the circuit arrangement 10 contains, in theexemplary embodiment: a processor 40, for example constructed like acommercially available microprocessor, an encryption coprocessor 42,which operates for example in accordance with the RSA algorithm (Revist,Schamir and Adlemann) or in accordance with the DES algorithm (DataEncryption Standard), and a sensor array 44 having a plurality ofcurrent and voltage sensors and also having a plurality ofanalog-to-digital converters for converting the analog sensor signalsinto digital data.

In accordance with a first exemplary embodiment, the circuit blocks ofthe circuit arrangement 10 that are illustrated in FIG. 1 are dividedbetween two different substrates such that one substrate carries thesensor array 44 and all parts of the memory circuit apart from thecontrol circuit 38, that is to say all of the function blocks framed byonly a single border in FIG. 1, namely: the memory cell arrays 16, 18,the word line driver transistors 20, 22, the bit line driver transistors24, the word line decoding circuits 30, 32, the logic circuits 34, thecharge pump 36, and the sensors and converters of the sensor array 44.By contrast, in the first exemplary embodiment, the second substratecarries the function blocks surrounded by a double frame in FIG. 1,namely: the control circuit 38, the processor 40, and the encryptioncoprocessor 42.

Thus, only the control circuit 38 of the memory circuit is situated onthe second substrate, so that only a comparably small number ofelectrically conductive connections have to be produced between thecircuits on the two substrates, for example fewer than 100 connections,e.g. so-called soldering bumps. Bulk substrates or SOI substrates(silicon on insulator) may be used.

FIG. 2 shows a division of the function blocks of the circuitarrangement 10 between two substrates in accordance with a secondexemplary embodiment. In the second exemplary embodiment, one substratecontains the function blocks of the circuit arrangement 10 that aresurrounded by a single frame in FIG. 2, namely: the memory cell arrays16, 18, the word line driver transistors 20, 22, the bit line drivertransistors 24, the charge pump 36, and the sensors and converters ofthe sensor array 44. By contrast, in accordance with the secondexemplary embodiment, the second substrate contains the function blockssurrounded by a double frame in FIG. 2, namely: the word line decodingcircuits 30, 32, the logic circuits 34, the control circuit 38, theprocessor 40, and the encryption coprocessor 42.

In the second exemplary embodiment, the number of connections betweenthe two substrates is very large, since each word line and each bit lineof the memory circuit is assigned a connection. By way of example,several thousand connections connect the two substrates.

FIG. 3 shows a cross section through a substrate stack 50 during theproduction of a circuit arrangement containing, by way of example,function blocks that are identical or similar to those of the circuitarrangement 10. The substrate stack 50 contains a lower bottom substrate52, an intermediate substrate 54 arranged above the bottom substrate 52,and a top substrate 56 arranged above the intermediate substrate. In thecase of the production state illustrated in FIG. 3, the bottom substrate52 is still part of a semiconductor wafer containing a multiplicity ofbottom substrates 52 which are separated from one another at the end ofthe production process. By way of example, the bottom substrate 52 is atleast twice as thick as the intermediate substrate 54 or the topsubstrate 56. In a first exemplary embodiment, the intermediatesubstrate 54 and the top substrate 56 have already been singulated. Inanother exemplary embodiment, the intermediate substrate 54 is part of asemiconductor wafer carrying a multiplicity of intermediate substrates54. The top substrate 56 is part of a semiconductor wafer carrying amultiplicity of top substrates 56. In this case, the intermediatesubstrate 54 and the top substrate 56 are singulated together with thebottom substrate 52.

The bottom substrate 52, the intermediate substrate 54 and the topsubstrate 56 carry interconnects 62, 64 and 66, respectively. In theexemplary embodiment, the interconnects 62, 64 and 66 are situated onthe upper area of the bottom substrate 52, of the intermediate substrate54 and of the top substrate 56, respectively. In other exemplaryembodiments, there are a plurality of layers of interconnects in eachsubstrate. In a further exemplary embodiment, interconnects are alsosituated on the rear sides of the bottom substrate, of the intermediatesubstrate and/or of the top substrate 56. The interconnects of differentsubstrates 52 to 56 are interconnected by vertical metallizations 68,for example by a metallization between the bottom substrate 52 and theintermediate substrate 54 or by a metallization (not illustrated)between the top substrate 56 and the bottom substrate 52.

An insulating spacing, filled for example by a solid dielectric, forexample by silicon dioxide, is situated between the bottom substrate 52and the intermediate substrate 54 and also between the intermediatesubstrate 54 and the top substrate 56. Parts of a memory circuit aresituated on the bottom substrate 52, for example. Other parts of thesame memory circuit are situated on the intermediate substrate 54, bycontrast.

FIG. 4 shows a plan view of a layer stack 70 containing a bottomsubstrate 72 and a top substrate 74 arranged thereabove. Furthersubstrates are not contained in the layer stack 70. By way of example,the function blocks framed by a single border in FIG. 1 are situated onthe bottom substrate 72 and the function blocks framed by a doubleborder in FIG. 1 are situated on the top substrate 74. Along itsperiphery, the bottom substrate 72 carries bonding islands 76 for theconnection of bonding wires which are intended to lead to connectionpins of a housing for the encapsulation of the layer stack 70. Thebonding islands 76 have, for example, a length of greater than 50 μm(micrometers) and a width of greater than 50 μm, typically of 100 μm ineach case.

Situated between the bottom substrate 72 and the top substrate 74 aree.g. three rows of soldering connections 78, a total of 24 solderingconnections 78 in the exemplary embodiment. The soldering connections 78end on soldering islands which, by way of example, have a width of lessthan 20 μm and a length of less than 20 μm, typically a size of 10 μm×10μm. The soldering connections 78 are produced in the context of a rapidchip mounting technique, also referred to as flip-chip technique or asface-to-face technique.

FIG. 5 shows a cross section through the substrate stack 70 along aseries of soldering connections 78. Interconnects 80 carried by thebottom substrate 72 are situated opposite interconnects 82 carried bythe top substrate 74.

In other exemplary embodiments, the function blocks of the circuitarrangement 10 are divided between the two substrates in a differentmanner than that explained above. In further exemplary embodiments, thecircuit arrangement 10 also contains other function blocks.

The production methods explained above can be used highly beneficiallyin particular when technologies with minimum feature sizes of less than250 nm (nanometers) and in particular less than or equal to 65 nm areproduced.

Accordingly, a circuit arrangement which has hitherto been produced onone chip is divided into two or more partial chips optimally with regardto the production outlay. The partial chips are then connected throughthree-dimensional integration. The performance of the product remainsthe same or is even increased. The selection criterion is chosen suchthat each partial chip contains only a limited number of mutuallydifferent components.

The table below shows a comparison of process steps between an embeddedprocess listed in column 1, in which a nonvolatile memory circuit with aprocessor is arranged on one chip, and the method presented hereinlisted in columns 2 and 3, in which two partial chips are produced andconnected later.

TABLE 1 Column 1 (embedded) Column 2 (memory) Column 3 (logic) STI(shallow trench DTI (deep trench STI (shallow trench insulation)insulation) insulation) High-voltage (HV) n- High-voltage (HV) n- typewell type well HV p-type well HV p-type well Medium-voltage (MV)Medium-voltage (MV) Vt implantation Vt implantation Tunnel window Tunnelwindow Floating gate (FG) Floating gate (FG) LG - region by region LG -region by region removal of the FG's removal of the FG's n-type welln-type well p-type well p-type well Dual gate oxide Dual gate oxideStacked gate etch Stacked gate etch Matrix implantation Matriximplantation Gate patterning Gate patterning Gate patterning HV-n-LDDHV-n-LDD (low doped drain) (low doped drain) HV-p-LDD HV-p-LDD (lowdoped drain) (low doped drain) Logic NFET channel Logic NFET channelconnection (extension) connection (extension) Logic PFET channel LogicPFET channel connection connection n+ source/drain n+ source/drain n+source/drain p+ source/drain p+ source/drain p+ source/drain Silicideblocking Silicide blocking Silicide blocking Contact Contact ContactMetal 1 Metal 1 Metal 1 Metal 2 Metal 2 Metal 2 Via 1 Via 1 Via 1 Metal3 Metal 3 Metal 3 Via 2 Via 2 Via 2 Metal 4 Metal 4 Metal 4 Via 3 Via 3Via 3 Via last copper layer Via last copper layer to the interconnect tothe interconnect AlCu transfer pad AlCu transfer pad TV (opening of theTV (opening of the passivation to the passivation to the connectionpads) connection pads)

The processes in accordance with columns 2 and 3 of the table are lesscomplex than the process in accordance with column 1 when considered bythemselves in each case and also when considered altogether. Theprocesses in accordance with columns 2 and 3 may be carried out atdifferent production sites.

By way of example, the production—optimized for rapidity—of thenonvolatile circuit in accordance with column 2 with an aluminummetallization and an oxide intermetal dielectric is carried out at aproduction site A. By contrast, the production of the logic circuit inaccordance with column 3 with copper metallization and a dielectrichaving a low dielectric constant of less than 3.9 is carried out at aproduction site B. This procedure results in a considerable reduction incosts compared with the method in accordance with column 1. Moreover, inthe case of the partial chip for the memory circuit, it is possible touse deep trench isolations for optimizing the area taken up. Such deeptrenches cannot readily be produced together with the shallow trenchisolations required for the logic circuit. Accordingly, there is aconsiderable reduction in the costs per mm² (square millimeter) ofsilicon substrate. The costs for the connection of the subcircuits, forexample by means of the face-to-face technology, are small compared withthe cost saving as a result of the division into two processes.

The number of connections between the partial chips depends on thedivision. In the case of the memory circuits, the word line and bit linedecoders contain logic transistors. In the case of the first exemplaryembodiment explained above, both partial chips contain logictransistors. The division chosen, however, enables a simple interfacewith approximately 80 connections. However, the process complexity ishigher than in the second exemplary embodiment.

The second exemplary embodiment involves separation through the wordline section and through the bit line section. The logic transistors forthe word line and bit line decoders are arranged on the logic circuitchip, whereas the high-voltage and medium-voltage transistors arearranged on the cell array substrate. The process complexity in the caseof the second exemplary embodiment is considerably lower than theprocess complexity in the case of the first exemplary embodiment.However, more connections are required between the substrates. Thesecond exemplary embodiment is the preferred one from the standpoint ofcosts. The large number of connections can be realized without any lossor with an acceptable loss in terms of the access time of the memorycircuit or generally in terms of performance.

In both exemplary embodiments, however, the total costs for productionare considerably less than the costs for a corresponding embeddedtechnology. This is also true for very small chip areas, e.g. with a sumof the chip area of the two substrates of less than 5 mm².

The method can be applied not just to the separation of memory circuitsbut also to other circuits that have hitherto been produced only on asingle substrate, for example: BICMOS circuits (Bipolar ComplementaryMetal Oxide Semiconductor) can be separated into CMOS circuits on onesubstrate and bipolar circuits on the other partial substrate, or astandalone flash can be divided into the state machine on one partialchip and the cell array and also the decoders on another partial chip.

The methods explained can be used for the production of circuits on aplurality of substrates particularly when innovative methods are usedfor producing a processor with minimum feature dimensions of less thanor equal to 65 nm. These technologies are virtually incompatible withthe requirements made of technologies for the production of flash memorycircuits.

Moreover, high-voltage or medium-voltage transistors, on account ofphysical stipulations, cannot benefit from a reduction of the minimumfeature size, that is to say that the expensive masks for producing thelogic circuits would have no advantage for the production of the memorycircuits. This also applies to digital signal processors in which theanalog components or circuits do not benefit from the reduction of theminimum feature size for the logic circuit of the digital signalprocessor. These disadvantages can be avoided by virtue of the divisionbetween partial substrates.

By contrast, it is possible to produce logic transistors havingthreshold voltages in the lower, medium and upper voltage range, of e.g.0.1 V (volt), 0.3 V and 0.5 V, respectively, on one substrate, e.g. onthe logic substrate for the processor 40 and the coprocessor 44.

In particular, problems relating to a gate dielectric having adielectric constant of greater than 3.9 can be solved more simply byvirtue of a skillful division between a plurality of chips. Inparticular, problems in the chemical mechanical polishing of the stackedgate electrodes, problems in the realization of a dielectric having ahigh dielectric constant based on an ONO stack (oxide nitride oxide), inparticular with regard to the data retention time, problems ofavailability of an anisotropic etching method for these dielectrics, inparticular an anisotropic ion etching method, and problems in therealization of sidewall oxidation, e.g. the dielectric mightcrystallize.

In addition, other problems that can be solved include problems withintermetal dielectrics having dielectric constants of less than 3.9, forexample the suitability thereof for higher voltages or problems whenbonding onto thin interconnects situated in a dielectric having a lowdielectric constant, problems with the stressing of the silicon, forexample the thermal instability of the silicon that is stressed onaccount of an ONO method (if the top oxide of the ONO stack is replacedby a high-temperature oxide, the thermal instability of the stressedsilicon on account of the sidewall oxidation, and stressing of thesilicon as a result of dislocations which influence the data retentiontime), problems with raised source or drain zones and the associatedincrease in the so-called moving bit rate, and problems with SOItechniques, in particular integration on partly depleted or fullydepleted SOI substrates or integration on silicon-germanium.

It is therefore intended that the foregoing detailed description beregarded as illustrative rather than limiting, and that it be understoodthat it is the following claims, including all equivalents, that areintended to define the spirit and scope of this invention. Nor isanything in the foregoing description intended to disavow scope of theinvention as claimed or any equivalents thereof.

1. A method for producing an integrated circuit arrangement, in whichthe following steps are performed without any restriction by the orderspecified: fabricating an integrated memory cell array on a memory cellarray substrate using a first sequence of method steps; fabricating anintegrated logic circuit that provide basic functions of the memory cellarray on a logic circuit substrate, which is separate from the memorycell substrate, using a second sequence of method steps, which differsfrom the first sequence; arranging the integrated memory cell array andthe integrated logic circuit to form a memory circuit arrangement,wherein a main area of the integrated memory cell array and a main areaof the integrated logic circuit lie in two planes parallel to oneanother and overlapping one another in a direction normal to the mainarea; wherein the number of connection between the substrates depends onthe number of word lines and/or bitlines and the number of connection isgreater than 1000; wherein the logic circuit includes at least one of: acontrol circuit contained in the memory circuit, the control circuitcontrolling sequences when at least one of reading, writing or readingand writing content of a memory cell of the memory cell array, or adecoding circuit contained in the memory circuit, the decoding circuitselects, in a manner dependent on an address datum, a word line or a bitline connected to a plurality of memory cells of the memory cell array.2. The method as claimed in claim 1, wherein at least one of: the firstsequence contains at least one of the following method steps which isnot contained in the second sequence: producing deep trenches, producingat least one of: a n-type well or n-type layer or a p-type well orp-type layer for voltages of greater than 6 volts, producing a tunneloxide, producing insulated electrodes between two oxide layers, removingselected electrodes above the insulated electrodes, producing oxideregions having a thickness of greater than 50 nm, or producing channelconnection zones for voltages of greater than 6 volts, or the secondsequence contains at least one of the following method steps which isnot contained in the first sequence: producing shallow trenches,producing at least one of: a n-type well or n-type layer or a p-typewell or p-type layer for voltages of less than 5 volts, producingchannel connection zones for voltages of less than 5 volts, producing atleast one metallization layer more than in the first sequence.
 3. Themethod as claimed in claim 2, wherein at least one of: the deep trencheshave a depth of greater than 1 μm, the at least one of the n-type well,n-type layer, p-type well, or p-type layer for voltages of greater than6 volts has a doping gradient suitable for the voltages of greater than6 volts at an edge, the shallow trenches have a depth of less than 1 μm,the at least one of the n-type well, n-type layer, p-type well, orp-type layer for voltages of less than 5 volts is formed for voltages ofless than 2.5 volts, the channel connection zones are formed forvoltages of less than 2.5 volts.
 4. The method as claimed in claim 1,further comprising arranging the memory cell substrate and the logiccircuit substrate using at least one of a rapid chip mounting techniqueor a 3D integration method.
 5. The method as claimed in claim 1, whereinthe memory cell is a DRAM memory cell, a SRAM memory cell, a ROM memorycell, an EEPROM memory cell, or a flash memory cell having an ONO layer.